error! too many detail props emitted on this map!Description:
The amount of detail props (the grasses and such that automatically appear on displacements with certain textures) has exceeded the maximum number of allowable detail props.

Solution:
Either reduce the amount of textures/displacements which cause these props to appear, or edit the texture's vmt's to decrease the number of detail props those textures emit.

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and:

fastvis = trueDescription:
You seem to be running vvis in -fast mode. This is okay for testing purposes, but mind that this will cause:

Strange compile errors, like 'cluster saw into cluster' errors

Strange errors ingame (including unexpected crashes)

Hitting limits ingame, by skipping essential optimization processses

Lower performance ingame

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This means
a) You have a huge amount of dispalcements that seem to use too many details. In this case you can probably come away with the solution given by the error message.
b) As you can see in the second error, the interlopers website warns you, that if you use fast vvis you can hit limits ingame. I'm not sure if the detailed props are meant with it, but it's definitly worth trying to run a normal compile for your map before reworking it.